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Synthesis 1987; 1987(10): 893-895
DOI: 10.1055/s-1987-28112
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Polarized Ketene Dithioacetals; 55:1 Synthesis of Novel 5-Aryl-2-methylthio-4H-pyran-4-ones from Cinnamoylketene Dithioacetals

B. Deb* , C. V. Asokan, H. Ila, H. Junjappa
  • *Department of Chemistry, North-Eastern Hill University, Shillong 793003, Meghalaya, India
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Publication Date:
12 September 2002 (online)

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A novel method for the synthesis of 5-aryl-2-methylthio-4H-pyran-4-ones 4a-h has been developed from the corresponding cinnamoylketene dithioacetals 1a-h in three successive steps. In the first step, 1a-h were oxidized with alkaline hydrogen peroxide to give the corresponding (β-aryl-,α,β-epoxypropanoyl)ketene dithioacetals 2a-h in 78-89% overall yields. In the second step the epoxyketones 2a-h were subjected to rearrangement in the presence of ether-boron trifluoride complex to give the corresponding (α-formyl-α-phenylacetyl)ketene dithioacetals 3a-h, which were then cyclized in the third step by refluxing in acetic acid/ethanol to afford the title compounds in good yields.